In order to simplify the description mostly photovoltaic generators will be used as receivers. In principle the tracking device is applicable to all devices, which trace a curved path. These include all the versions of solar devices which have to be aligned to the corresponding direction of the sunbeams, e.g., solar cookers and heliostats. The tracking device can also be used to track astronomical instruments (telescopes, antennae), to compensate the earth's rotation. Besides this, it is also applicable in the construction of machines and instruments, when an apparatus has to track an object, which traces a curved path. Examples of these are apparatus for working, mounting, transportation, identification or measuring, which have an effect on objects, which trace a curved path. Further it can for example trace moving objects, parts, griffers, filling devices or other moving apparatus (e.g., workpieces, tools and containers).
Due to the cost of the tracking, solar devices are often permanently mounted. Till now the tracking devices are mostly installed for radiation concentrating systems to adjust them according to the radiation direction. When the generator is moved around an axis which lies parallel to the earth's axis (equatorial mounting), the generator traces the sun's position through a simple rotation with the speed of 15.degree. per hour. Such mountings are also used for telescopes. Depending on the seasonal differences in the paths of the sun the inclination of the generator to the axis is corrected periodically. Although their efficiency is simple they still need a cumbersome structure, because the slant of the rotating axis is determined by the latitude. Therefore solar apparatus often are mounted only on either a vertical or a horizontal axis, whereby a part of the utilizable energy is wasted. Further, the use of 2 axes, a vertical and a horizontal, with separate controls for the movement of each of the axes is already known. This device, however, requires additional expenses for the tilt of the horizontal axis. In very heavy telescopes, the equatorial mounting has been discarded and mounting on both, a vertical and a horizontal axis was applied. Similar solutions are known for tracking in machine and apparatus construction. In the case of robots, with separate controls for the movement of the several axes, problems with heavy tracking apparatus and high precision requirements make their construction for greater capacity and high rigidity troublesome.
German Offenlegungschrift No. 22 42 880 shows how the movement of points on the outer ring of a bearing set parallel to the equatorial plane can be transmitted to a telescope through a paralellogram guide. The telescope mount is mounted so that it rotates about one vertical and one horizontal axis, whereby difficulties in observing the sky in the vicinity of the poles are avoided. The large bearing required, disposed about the vertical shaft, and the large number of drive elements required, however, resulting in high cost.
French Pat. No. 24 80 002 describes a rod by means of which a parallactically mounted device is adjusted as a function of the declination of the object. Adjustment is made via a spindle on the hour axis, so that the spindle nut acts through the rod to achieve the desired diagonal position relative to the main axis.
U.S. Pat. Nos. 1,642,545 and 3,656,844 describe drives which produce an additional movement corresponding to the elevation or declination of the sun in the rotation of heliostats about the main axis. In U.S. Pat. No. 1,642,545 the main axis is vertical; an attempt is made to derive the position of the reflector corresponding to the daily and seasonal variations in the elevation with gear drives from a continuous azimuthal motion. U.S. Pat. No. 3,656,844 is based on a parallactically mounted main axis, so that only the seasonal change in the position of the sun is adjusted. Two reflectors are provided for the purpose, used alternately. The seasonal variation occurs automatically, using a combination of gear, curve, and plane coupled drives. The desired adjustment is achieved by shifting the two entrained coupling articulation points. In both cases, the expense required both for manufacture and construction is very high.
Regulation of tracking drives based on the measured deviation from exact alignment is described for example by A. E. Whitford and G. E. Kron (R.S.I, Vol. 8, March 1937, pp. 78/82). A drive with regulation is required for each axis. Additional measures are required to align the device approximately at the outset.
A precise tracking is important for concentrating solar devices and for heliostats and often in mechanical engineering. For other receivers a precise tracking is not necessarily required, because the impinging energy is proportional to the cosine of the angle between the receiver normal and the direction of the sunbeams, which has an neglegible deviation from 100% for small angles. Because of the cooling-effect through natural convection and to improve the capacity during the day, even at very high sunposition, a minimum angle (e.g., 30.degree.) may be desirable.